Easy opening end

ABSTRACT

This invention relates to the attachment of a pull tab to an easy opening end for cans and like receptacles by means of a novel rivet formation wherein the head of the rivet is of a thickness substantially approaching the original thickness of the material of the end. The rivet is formed in two punching steps each employing a flat headed punch.

United States Patent 1191 Enjolras et a].

1451 July 30, 1974 EASY OPENING END [75] Inventors: Christian Enjolras, Pavillons-S-Bois;

Pierre Gautier, Ville-D Avray; Emile Billy, St-Cloud, all of France [73] Assignee: Etablissements J. J. Carnaud & Forges De Basse-Indre, Paris, France [22] Filed: Jan. 15, 1973 [21] Appl. No.: 323,718

Related U.S. Application Data [62] Division of Ser. No. 191,731, Oct. 22, 1971, Pat. No.

[52] U.S. Cl. 220/54 [51] Int. Cl B65d 17/20 [58] Field of Search 220/54, 48; 113/121; 29/509, 522

[56] References Cited UNITED STATES PATENTS 3,602,980 9/1971 Heffner 220/54 X Primary Examiner-George T. Hall Attorney, Agent, or Firm-Diller Brown, Ramik & Wight [5 7] ABSTRACT This invention relates to the attachment of a pull tab to an easy opening end for cans and like receptacles by means of a novel rivet formation wherein the head of the rivet is of a thickness substantially approaching the original thickness of the material of the end. The rivet is formed in two punching steps each employing a flat headed punch.

3 Claims, 8 Drawing Figures 1 EASY OPENING END This application is a division of my copending application Ser. No. 191,731, filed Oct. 22, 1971, entitled EASY OPENING END AND METHOD OF FORM- ING SAME now US. Pat. No. 3,781,972.

The present invention relates generally to the securing of a pull ring on a metallic, easy opening end for a food can or other receptacle.

As is known, so-called easy opening ends comprise one or more weakening lines which define a zone or panel portion that is detachable by a simple pulling operation, and present a pull ring intended to permit the exercising of such pulling on the panel portion.

The present invention more paticularly relates to the technique according to which the securing of this pull ring to the end that supports it is effected by means of a rivet formed in the actual body of the end.

BACKGROUND OF THE INVENTION According to this technique, which is well known, there is applied to the end in question a series of punching operations which lead in a first step to the formation of a boss, then in a second step to the formation of a stud from the material of the boss, but of generally lesser dimensions; a pull ring is then engaged on the stud by an opening provided for this purpose on the pull ring, and finally a riveting operation is effected on the stud.

The punching operations are conducted in two stages in order to make the stress on the metal, which is the top on which the punching operations are effected, more gradual, and thus to avoid elongation of the metal which could ultimately cause cracks or ruptures.

For certain materials it has even been proposed to effect these punching operations in three different successive stages, going from the formation of the initial boss to the ultimate formation of the stud with an intermediate bossing between the operation for the initial boss and that of the final stud.

In all cases the first punching operation is effected at present using a punch with a substantially hemispherical head, whereas the head of the final stud which is to be obtained must be substantially flat.

In all cases also the riveting operationis effected with use of an anvil whose height is only slightly less than that of the stud which is to be riveted.

There are numerous drawbacks to this procedure.

To begin with, the hemispherical form of the boss which is obtained as a result of the first punching operation necessarily requires that the height of this boss is considerably greater than that of the stud which is to be produced ultimately.

Consequently, there is inevitably a certain thinning of the metal at the top part of this boss and, in practice, this thinning of the metal is progressively accentuated during the second punching operation, and then the riveting operation which follows, as it is done by present day techniques, causes a not insignificant creep of the metal from the center of the rivet toward the periphery, which can only accentuate the risk of fracture in this zone.

Furthermore, the size of the boss obtained at the conclusion of the first punching operation can cause a local deformation of the end. More exactly, if one refers to an end which is intended to be seamed onto the cylindrical wall of a can body and has a cylindrical wall or chuck wall engageable with the can body, it is not unusual that the boss in question will cause an accidental deformation of the chuck wall. Such a deformation can, onthe one hand, ultimately disturbs the seaming operation and, on the other hand, it can be the starting point for more serious deformation in the subsequent processes of storage of the can. Thus, this deformation of the chuck wall may require discarding of the can which is so effected.

SUMMARY OF THE INVENTION The present invention is intended first in a general way to provide a process which will eliminate these drawbacks.

In a first aspect, a process of the invention for securing of a pull ring on a metallic, easy opening end of a food can or other receptacle is of the type according to which there are effected, with reference to the said top, punching operations which lead in a first step to the formation of a boss; next in a second step to the formation of a stud from the material of the boss, but of generally lesserdimensions, then engagement of the pull ring on the said stud by means of an opening provided for this purpose in the pull ring, and riveting of the stud, characterized in that the first punching operation is effected by means of a punch with a substantially flat head, the boss which is obtained from this first punching operation having preferably a height which is substantially that of the stud which is to be produced.

According to a second aspect, the process of the invention is characterized in that the riveting operation is effected by means of an anvil whose height is at the most 60 per cent, preferably less than 50 per cent, of

the height of the stud.

The applicant has found that he can limit the thinning of the metal in the treated zone to the greatest possible extent, and for this purpose, the process of the invention also is characterized in that the punching and riveting operations are conducted in such a way that the difference of thickness of the head of the stud after riveting, as compared to the thickness of the rest of the end is less than 20 per cent and preferably at the most equal to 10 per cent of the thickness of the end.

This advantageous result can be attributed partly to the relative shallowness of the boss produced in the first punching operation and partly to the large space which exists between the stud produced by the second punching operation and the anvil used for the riveting, the riveting thus being effected rather more by folding of the stud than by lateral deformation of the metal of the stud.

Furthermore, the process of the invention advantageously allows complete avoidance of any accidental deformation of the end to which it is applied, especially any deformation of its chuck wall.

Moreover, the process of the invention advantageously allows an especially effective fastening of the pull ring on the end that supports it, the pull ring being either fastened directly flat on the end, all around the opening by which it is engaged on the rivet on the end, without the necessity of providing on the end a boss of any kind for angular locking of the pull ring.

Finally, the process of the invention, which requires only two punching steps for production of the riveting stud, is advantageously suited for the treatment of any kind of metallic end, whether it be made of aluminum, with or without coating, of tin, or steel possibly with some protective coating, such as chrome and/or lacquer.

Thus, the same facilities can readily be used for the treatment of ends of different kinds allowing the adaptation of various tools.

The present invention also relates to an easy opening metallic end for a food can or other receptacle furnished with a pull ring riveted according to the process which has been described above, as well as to food cans or other receptacles furnished with such an end.

The objects of the invention, their characteristics and advantages will become evident moreover from the following description which is given as example with reference to the attached schematic drawings in which:

FIG. 1 is a perspective view of a can with an easy opening metallic end in accordance with the invention;

FIG. 2 is an enlarged fragmentary sectional view taken generally along line Il-II of FIG. 1;

FIGS. '3, 4, 5, 6 are schematic sectional views illustrating the various steps of the process which effect the riveting according to the invention of a pull ring onto a metallic end for a can;

FIG. 7 is an enlarged fragmentary sectional view of a pull ring riveted according to the invention onto such an end;

FIG 8 is a view similar to FIG. 7 and shows by way of comparison the results of the earlier technique in this art.

In FIG. 1 there is shown a can 10 equipped with an easy opening end 11 seamed onto the cylindrical wall or body 12 of can 10. The end 11 presents peripherally a score line 13 near the cylindrical chuck wall 14 by which it is secured against the body 12 of the can. The end 11 includes a pull ring 15.

The pull ring has an opening 16 by which it is secured on a rivet l7 drawn from the material of the end 11.

The invention concerns the process for producing and setting the rivet 17. Y

According to a first aspect of the invention, as shown in FIG. 3, end 11 is grasped between two dies 20A, 20B which have hollowed opposite passages 21A, 21B and the end 11 subjected to the action of a punch 23 whose head 24 is substantially flat, the punch 23 being movable in the passages 21B, 21A.

Boss 25 with flat head is thereby formed.

According to a supplementary characteristic of the invention, height H1 of the boss 25, which is considered as being the depth of the punching pass that produced it, is substantially equal to or greater by less than 20 per cent of the height H2 of a stud 27 that is to be produced for the rivet, said height being defined in the same conditions.

More precisely stated, we have for example a treatment of an end made of metal with a thickness of 0.22 mm, the height H1 of boss 25 as defined above is then for example of the order of about 2.15 mm.

End 11 is then subjected to a second punching operation as shown in FIG. 4, intended to reduce the general dimensions of boss 25 and thus transform it into the stud 27 which can be used as a rivet.

This punching operation is conducted in a manner discussed above by engagement of end 1 1 between two dies 28A, 288 having passages 29A, 29B opposite each other and by the use of a flat head punch 30 which moves in the passages 29A, 29B.

- With reference to the end described in the above example, the hieght H2 of the stud 27 thus obtained is, for example, of the order of about 2 mm.

Preferably the active part of punch 30 has a diameter which is substantially less than that of passage 29A with which it cooperates, so that stud 27 has a side wall 32 which is tapered.

End 11 is then positioned by its stud 27 on an anvil 33, sitting in the position to which it is guided by the slope of side wall 32 of the stud 27.

According to a principle or supplementary characteristic of the invention, height H3 of anvil 33 is substantially less than height H2 of stud 27.

This height H3 is no greater than 60 per cent and preferably is less than 50 per cent of height H2 of the stud.

If we have a metal end as in the above example, this height H3 is, for example, of the order of 0.8 mm.

The anvil 33 is in contact with side wall 32 of stud 27 between the base and the top of the stud 27 along the periphery of the anvil 33. Pull ring 15 is then engaged by its opening 16 on stud 27 and then die 35 is applied all around the opening 16, as shown in FIG. 5.

In passage 36 of die 35, there slides a punch 37 which effects the riveting of stud 27 over the pull ring 15 all around opening 16 of the pull ring, as shown in FIGS. 6 and 7. In general, reference numeral 39 designates the rivet thus obtained and reference numeral 40 designates the top part or head of the rivet 39.

It should be noted that this riveting is effected almost exclusively by folding of side wall 32 of stud 27 in a circular movement toward the inside of this wall without any great amount of creep in the metal. We can attribute this result, which is especially advantageous, to the use of an anvil which allows the existence of an appreciable distance between it and the head of the stud which is to be riveted. The advantage that results from it is especially that the thinning of the top part 40 of rivet 39 formed from the stud 27 is very slight.

Taking into account the fact that the thinning resulting from the'punching operations of the invention is also very slight, because of the flat form of the punches and the relatively shallow depth of the pass of the first of these punching operations, thickness E2 of the top part 40 of rivet 39, as shown in FIG. 7, is only a little less than thickness E1 of the rest of the end.

In practice, because of this invention, the difference in thickness Ell-E2 remains less than 20 per cent and is preferably at the most equal to ID per cent of thickness E1.

With the end given as an example above, whose initial thickness E1 is 022mm, thickness E2 of the top part 40 of rivet 39 is, for example about 0.20 mm.

In order better to stress the importance of this result, whose advantages are to avoid the presence of a weaker zone at the level of the rivet, it is pointed out that the thinning of the top zone of such a rivet currently, according to prior technique, reaches 30 per cent or even 50 per cent, which corresponds to a much greater elongation of the metal and hence greater fatigue.

This greater thinning shows clearly in FIG. 8, which is given as example, showing an end treated according to prior technique with three successive punching operations, the first two being effected by hemispherical punches.

It is to be noted also, in comparing FIGS. 7 and 8, that the process of the invention allows direct fixation of pull ring on end 11. The pull ring is seated on the end all around the ring opening 16 and therefore, the securement of the pull ring is sufficiently effective to insure the desired angular locking of the pull ring relative to the rivet 39.

In accordance with the former technique, the results of which are shown in FIG. 8, it is customary, in order to insure such a locking, to provide bosses, such as bosses 50, which project from end 11.

Finally, tests have shown that in securing operations according to the invention of a pull ring 15 on an end 11 with a cylindrical chuck wall 14, no accidental deformation of this chuck wall is observed.

Although only a preferred embodiment of the rivet formation is discussed herein, it is to be understood that the invention is not so limited, and minor variations may be made without departing from the spirit and scope of the invention as defined by the appended claims.

We claim:

1. An easy opening end for a can or other receptacle characterized in that a pull ring is secured to a removable panel portion of said end by an integral rivet having' a top wall wherein the difference in thickness of said top wall as compared to the thickness of the rest of said end is less than 20 per cent of the thickness of said end, and wherein said top wall has a central portion defining a major part of the diameter of the top wall which is free of evidence of bending stresses and wherein said major part shows evidence of primarily tensile stresses.

2. The easy opening end of claim 1 wherein said thickness difference is a maximum of 10 per cent of the thickness of said end.

3. The easy opening end of claim 1 wherein said pull ring has an opening receiving said rivet, said pull ring around said opening being flatly seated on said end, and said rivet locking said pull ring against pivoting around said rivet. 

1. An easy opening end for a can or other receptacle characterized in that a pull ring is secured to a removable panel portion of said end by an integral rivet having a top wall wherein the difference in thickness of said top wall as compared to the thickness of the rest of said end is less than 20 per cent of the thickness of said end, and wherein said top wall has a central portion defining a major part of the diameter of the top wall which is free of evidence of bending stresses and wherein said major part shows evidence of primarily tensile stresses.
 2. The easy opening end of claim 1 wherein said thickness difference is a maximum of 10 per cent of the tHickness of said end.
 3. The easy opening end of claim 1 wherein said pull ring has an opening receiving said rivet, said pull ring around said opening being flatly seated on said end, and said rivet locking said pull ring against pivoting around said rivet. 